Piwigo costs money. A hosting plan at piwigo.com would cost us
300€/year (according to their tariff). And soon we would have more
than 50 GB.

People would need to register an account on our site in order to
write comments or upload photos

Not sure whether it is possible to upload photos from a mobile phone.

The advantages of Piwigo versus Google are very abstract: We would
not depend on Google. We would not even depend on Piwigo.com because
we could decide at any time to set up and run our own server.

Okay it is clear that Piwigo has no chance against Google here in
Vigala. If I’d suggest a solution using Piwigo for our village photo
collection, my friends here would ask why I want them to use such a
system instead of the “free” Google system. And I guess that in Eupen
it wouldn’t be different. Normal people just prefer to rely on Google
or Facebook because that gives them all they need. “We want free beer,
we don’t need no free speach.”